1. The document discusses tools used to study electromagnetic radiation and space, including refracting and reflecting telescopes, radio telescopes, and space telescopes like Hubble. 2. It also describes the structure and activity of the Sun, including its photosphere, chromosphere, corona, sunspots, prominences, and solar flares. 3. The Sun's energy is produced through nuclear fusion, which converts hydrogen to helium in its core and will allow it to exist stably for billions of years.

1. Chapter
1515
Studying the Sun

2. Electromagnetic Radiation
24.1 The Study of Light
 Electromagnetic radiation includes gamma
rays, X-rays, ultraviolet light, visible light,
infrared radiation, microwaves, and radio
waves.
 The electromagnetic spectrum is the
arrangement of electromagnetic radiation
according to wavelength.

3. Electromagnetic Spectrum

4. Electromagnetic Radiation
24.1 The Study of Light
 Nature of Light
• In some instances light behaves like waves, and
in others, like particles. In the wave sense, light
can be thought of as swells in the ocean. This
motion is characterized by a property known as
wavelength, which is the distance from one wave
crest to the next.
 Photons
• A photon is a small packet of light energy.

5. Spectroscopy
24.1 The Study of Light
 Spectroscopy is the study of the properties
of light that depend on wavelength.
 Continuous Spectrum
• A continuous spectrum is an uninterrupted
band of light emitted by an incandescent solid,
liquid, or gas under pressure.

6. Spectroscopy
24.1 The Study of Light
 Absorption Spectrum
• An absorption spectrum is a continuous
spectrum produced when white light passes
through a cool gas under low pressure. The gas
absorbs selected wavelengths of light, and the
spectrum looks like it has dark lines
superimposed.

7. Spectroscopy
24.1 The Study of Light
• An emission spectrum is a series of bright lines
of particular wavelengths produced by a hot gas
under low pressure.
 Emission Spectrum
• When the spectrum of a star is studied, the
spectral lines act as “fingerprints.” These lines
identify the elements present and thus the star’s
chemical composition.

8. Formation of Spectra

9. The Doppler Effect
24.1 The Study of Light
 The Doppler effect is the apparent change
in frequency of electromagnetic or sound
waves caused by the relative motions of the
source and the observer.
 In astronomy, the Doppler effect is used to
determine whether a star or other body in
space is moving away from or toward Earth.

10. The Doppler Effect

11. Refracting Telescopes
24.2 Tools for Studying Space
 A refracting telescope is a telescope that
uses a lens to bend or refract light.
 Focus
• The most important lens in a refracting
telescope, the objective lens, produces an
image by bending light from a distant object so
that the light converges at an area called the
focus (focus = central point).

12. Keck Telescope

13. Simple Refracting Telescope

14. Refracting Telescopes
24.2 Tools for Studying Space
 Chromatic Aberration
• A chromatic aberration is the property of a lens
whereby light of different colors is focused at
different places.

15. Reflecting Telescopes
24.2 Tools for Studying Space
 A reflecting telescope is a telescope that
reflects light off a concave mirror, focusing
the image in front of the mirror.
 Advantages of Reflecting Telescopes
• Most large optical telescopes are reflectors.
Light does not pass through a mirror, so the
glass for a reflecting telescope does not have to
be of optical quality.

16. Viewing Methods with
Reflecting Telescopes

17. Reflecting Telescopes
24.2 Tools for Studying Space
 Properties of Optical Telescopes
• Both refracting and reflecting telescopes have
three properties that aid astronomers in their
work:
1. Light-gathering power
2. Resolving power
3. Magnifying power

18. Detecting Invisible Radiation
24.2 Tools for Studying Space
 Radio Telescopes
• A radio telescope is a telescope designed to
make observations in radio wavelengths.
• A radio telescope focuses the incoming radio
waves on an antenna, which, just like a radio
antenna, absorbs and transmits these waves to
an amplifier.

19. Radio Telescopes

20. Detecting Invisible Radiation
24.2 Tools for Studying Space
 Advantages of Radio Telescopes
• Radio telescopes are much less affected by
turbulence in the atmosphere, clouds, and the
weather.
• No protective dome is required, which reduces
the cost of construction.
• Radio telescopes can “see” through interstellar
dust clouds that obscure visible wavelengths.

21. Space Telescopes
24.2 Tools for Studying Space
 Space telescopes orbit above Earth’s
atmosphere and thus produce clearer
images than Earth-based telescopes.
• The first space telescope, built by NASA, was
the Hubble Space Telescope. Hubble was put
into orbit around Earth in April 1990.
 Hubble Space Telescope

22. Hubble Space Telescope

23. Space Telescopes
24.2 Tools for Studying Space
 Other Space Telescopes
• To study X-rays, NASA uses the Chandra X-Ray
Observatory. This space telescope was launched
in 1999.
• Another space telescope, the Compton Gamma-
Ray Observatory, was used to study both visible
light and gamma rays.
• In 2011, NASA plans to launch the James Webb
Space Telescope to study infrared radiation.

24. Images of the Milky Way Galaxy

25. Structure of the Sun
24.3 The Sun
 Because the sun is made of gas, no sharp
boundaries exist between its various layers.
Keeping this in mind, we can divide the sun
into four parts: the solar interior; the visible
surface, or photosphere; and two
atmospheric layers, the chromosphere and
corona.

26. Structure of the Sun
24.3 The Sun
 Photosphere
• The photosphere is the region of the sun that radiates
energy to space, or the visible surface of the sun.
• It consists of a layer of incandescent gas less than 500
kilometers thick.
• It exhibits a grainy texture made up of many small,
bright markings, called granules, produced by
convection.
• Most of the elements found on Earth also occur on the
sun.
• Its temperature averages approximately 6000 K
(10,000ºF).

27. Structure of the Sun

28. Structure of the Sun
24.3 The Sun
 Chromosphere
• The chromosphere is the first layer of the solar
atmosphere found directly above the
photosphere.
• It is a relatively thin, hot layer of incandescent
gases a few thousand kilometers thick.
• Its top contains numerous spicules, which are
narrow jets of rising material.

29. Chromosphere

30. Structure of the Sun
24.3 The Sun
 Corona
• The corona is the outer, weak layer of the solar
atmosphere.
• The temperature at the top of the corona
exceeds 1 million K.
• Solar wind is a stream of protons and electrons
ejected at high speed from the solar corona.

31. The Active Sun
24.3 The Sun
 Sunspots
• Sunspots appear dark because of their
temperature, which is about 1500 K less than
that of the surrounding solar surface.
• A sunspot is a dark spot on the sun that is cool
in contrast to the surrounding photosphere.

32. Sunspots

33. The Active Sun
24.3 The Sun
 Prominences
• Prominences are ionized gases trapped by
magnetic fields that extend from regions of
intense solar activity.
• Prominences are huge cloudlike structures
consisting of chromospheric gases.

34. Solar Prominence

35. The Active Sun
24.3 The Sun
 Solar Flares
• During their existence, solar flares release
enormous amounts of energy, much of it in the
form of ultraviolet, radio, and X-ray radiation.
• Solar flares are brief outbursts that normally
last about an hour and appear as a sudden
brightening of the region above a sunspot
cluster.
• Auroras, the result of solar flares, are bright
displays of ever-changing light caused by solar
radiation interacting with the upper atmosphere
in the region of the poles.

36. Aurora Borealis

37. The Solar Interior
24.3 The Sun
 Nuclear Fusion
• During nuclear fusion, energy is released
because some matter is actually converted to
energy.
• Nuclear fusion is the way that the sun produces
energy. This reaction converts four hydrogen
nuclei into the nucleus of a helium atom,
releasing a tremendous amount of energy.
• It is thought that a star the size of the sun can
exist in its present stable state for 10 billion
years. As the sun is already 4.5 billion years
old, it is “middle-aged.”

38. Nuclear Fusion